Reel lock mechanism of tape cassette, and tape cassette

ABSTRACT

Each lock portion ( 15 ) has a front portion ( 23 ) including an anchoring pawl ( 24 ) and a back portion ( 25 ) extending in a direction opposite to the front portion. Therefore, when a slider ( 14 ) withdraws, each back portion comes into contact with the inside surface of a back wall ( 10 ) of a cassette shell ( 4 ) and each lock portion rotates in an unlocking direction. 
     A bottom surface ( 109 ) defining each recess between engaging teeth ( 107 ) has a central portion which protrudes in a chevron shape. A corner of each protrusion has tapered surfaces ( 110 ′) and ( 110 ″). An anchoring pawl of each lock portion has a flat surface that comes into contact with one inclined surface ( 109 ′) of a chevron-shaped portion of any one of the recesses and one tapered surface ( 110 ′) of a protrusion disposed behind the adjacent recess.

TECHNICAL FIELD

The present invention relates to a reel lock mechanism of a tapecassette and a tape cassette using the reel lock mechanism. Morespecifically, the present invention relates to a technology forachieving size reduction of a tape cassette, for stabilizing operationof a reel lock, and for preventing reverse rotation of a tape reel whenthe tape reel is unlocked.

BACKGROUND ART

Ordinarily, a tape cassette rotatably accommodates two tape reels insidea cassette shell, with the two tape reels having a tape-shaped recordingmedium, such as a magnetic tape, wound thereupon.

There is a tape cassette comprising a reel lock mechanism for preventingrotation of the tape reels when the tape cassette is not loaded to atape drive device. By this structure, when the tape cassette is notloaded, even if, for example, vibration is exerted upon the tapecassette, a magnetic tape is prevented from becoming slack caused byrotation of the tape reels.

FIGS. 1 and 2 and FIGS. 23 to 28 illustrate a tape cassette b includinga related reel lock mechanism a. FIGS. 1 and 2 show the entire tapecassette b, and are also used to illustrate a first embodiment of thepresent invention described later. Of the symbols used, referencenumerals are used to denote component parts used in the presentinvention, while lower-case alphabetical letters are used to denotecomponent parts used in the related technology.

In the tape cassette b, two tape reels e and e upon which a magnetictape d is wound are rotatably accommodated inside a cassette shell c. Aplurality of engaging teeth f, f, . . . , serving as protrusions, areformed at the outer peripheral edge of a lower flange of each of thetape reels e and e, with recesses being formed therebetween (see FIGS.25 to 28).

The reel lock mechanism a is provided in a substantially triangularspace (hereinafter referred to as “the triangular space”), defined bythe back wall and the two reels e and e, inside the cassette shell c. Arectangular hole g is formed in a portion of the bottom surface of thecassette shell c where the reel lock mechanism a is situated. When thetape cassette b is loaded into a tape drive device, an insertion pin h,provided at the tape drive device, is inserted into the cassette shell cfrom the rectangular hole g, and acts on the reel lock mechanism a inorder to unlock the tape reels e and e (see FIGS. 25 to 28).

The reel lock mechanism a comprises a slider i, two lock portions j andj, a lock spring k, and a slide spring l (see FIGS. 23 and 24).

The slider i is supported so as to be movable forward and backwardinside the triangular space. Upwardly protruding support shafts m and m,which are separated in the leftward and rightward directions, areprovided at the back end of the slider i. A placement recess n, whichopens upward and backward, is formed between the support shafts m and mof the slider i (see FIGS. 23 and 24).

A pin insertion recess o for inserting the insertion pin h of the tapedrive device is formed in the bottom surface of a block situatedforwardly of the placement recess n in the slider i, with the lower halfof the back surface defining the pin insertion recess o being aninclined surface p which is displaced backward as it extends downward.

Lock portions j each comprise one plate member having a chevron shape asa whole in plan view. Cylindrical support portions q extendingvertically are integrally formed with the back edges of their respectiveplate members. The front ends of the two lock portions j and j extendaway from each other. Tapered anchoring pawls r and r are formed at thefront ends of the respective lock portions j and j (see FIGS. 23 and24).

Spring catch portions s are formed on the top side edges of therespective lock portions j between the support portions q and therespective anchoring pawls r. Lower side edges of the respective lockportions j have forms in which the front side portions thereof protrudedownward from substantially the longitudinal centers of the respectivelock portions j. The back edges of the respective downwardly protrudingportions are cam followers t which come into contact with respectivecams (described later) for rotating the respective lock portions j (seeFIGS. 23 and 24).

Externally fitting the support portions q to their respective supportshafts m of the slider i rotatably supports the lock portions j at theslider I (see FIGS. 23 and 24).

Anti-rotation portions are provided at the respective lock portions j,so that the angle of rotation in the direction in which they engage theengaging teeth f of the tape reels e does not become equal to or greaterthan a predetermined angle.

The lock spring k is a torsion coil spring, in which coil portions u andu, a linking portion v linking the coil portions u and u, and engagingportions w and w are integrally formed, with the coil portions u and ubeing separated in the leftward and rightward directions and theengaging portions w and w protruding from their respective coil portionsu and u and being positioned outwardly of the linking portion v. The twocoil portions u and u are supported at their respective support shafts mand m by being externally fitted to the top sides of the supportportions q and q of their respective lock portions j and j. The twoengaging portions w and w engage the spring catch portions s and s ofthe two lock portions j and j, so that the lock portions j and j arebiased in the directions in which the anchoring pawls r and r move awayfrom each other, that is, in the directions in which the anchoring pawlsr and r engage the engaging teeth f and f of the respective tape reels eand e (see FIG. 24).

The slide spring l is a helical compression spring, and is provided in acompressed manner between the inside surface of the back wall of thecassette shell c and the placement recess n of the slider i. By this,the slider i is biased forward (see FIGS. 25 to 28).

Ribs x and x having small heights measured from the bottom surface areprovided in a standing manner on both the left and right sides of theslider i inside the cassette shell c. In plan view, the ribs x and xcomprise portions extending in the direction in which the slider islides, portions which are one size larger than the outer peripheraledges of the respective tape reels e and e, and portions which arelocated in the paths of movement of the respective lock portions j andj. Of these portions, the portions located in the paths of movement ofthe respective lock portions j and j, more specifically, the portionssituated in correspondence with the respective cam followers t and t arecams y and y for controlling rotation of the respective lock portions jand j (see FIGS. 23 and 24).

When the tape cassette b is not loaded to a tape drive device, theslider i is biased forward, and the cam followers t and t of therespective lock portions j and j are separated from the respective camsy and y, so that the anchoring pawls r and r at the front ends of therespective lock portions j and j are rotated in the directions in whichthey move away from each other, and engage an engaging tooth f and anengaging tooth f of the respective tape reels e and e, thereby lockingthe tape reels e and e (see FIG. 25). In other words, the tape reels eand e are prevented from rotating in the direction in which the magnetictape d becomes slack.

Since the slider i is biased forward, a rotational force is applied tothe two tape reels e and e through the respective anchoring pawls r andr in the direction in which the magnetic tape d is tensioned, so thatthe magnetic tape d is maintained in a tensioned state when the tapereels e and e are locked.

When the tape cassette b is loaded into a tape drive device, theinsertion pin h of the tape drive device is inserted into the cassetteshell c from the rectangular hole g of the cassette shell c, and comesinto contact with the inclined surface p defining the pin insertionrecess o of the slider i (see FIG. 26(B)).

When the insertion pin h is further inserted into the pin insertionrecess o of the slider i, the front end of the insertion pin h pushesthe inclined surface p, so that the slider i moves towards the backagainst the biasing force of the slide spring 1 (see FIG. 27).

The cam followers t and t of the respective lock portions j and j comeinto contact with the respective cams y and y, and move towards the backalong the cams y and y, so that the lock portions j and j rotate in thedirection in which the anchoring pawls r and r move towards each other.By this, the anchoring pawls r and r of the respective lock portions jand j move away from the respective tape reels e and e, so that the tapereels e and e are unlocked, and are brought into a rotatable state (seeFIG. 28).

Next, FIGS. 1 and 2, FIGS. 14 to 17, and FIGS. 31 to 35 illustrate atape cassette b including another related reel lock mechanism a′. Thisrelated reel lock mechanism a′ differs from the above-described relatedreel lock mechanism a only in the forms of the cam followers. These camfollowers will be primarily described. Accordingly, the othercorresponding parts to those of the reel lock mechanism a will be giventhe same reference numerals, and will not be described below. Theoverall form of this tape cassette b is substantially the same as theabove-described tape cassette b. Accordingly, the reel lock mechanismillustrated in FIGS. 1 and 2 is labeled a′, and a general descriptionthereof will not be given below.

FIGS. 14 to 17 are also used to illustrate a second embodiment of thepresent invention described later. Of the symbols used, referencenumerals are used to denote the component parts used in the presentinvention, while lower-case alphabetical letters are used to denote thecomponent parts used in the related technology. Of the forms of thecomponent parts shown in FIGS. 14 and 15, the forms of anchoring pawls,which are front end portions of respective lock portions, are those usedin the second embodiment of the present invention. The second embodimentdiffers from the related technology only in the forms of the anchoringpawis. The forms of the anchoring pawls, which are front end portions ofrespective lock portions, used in this different related technology areshown in FIGS. 31 to 35.

Spring catch portions s are integrally formed with the top edges ofrespective lock portions j between support portions q and respectiveanchoring pawls r (see FIGS. 14 and 15). Downwardly protruding pins areformed at the inner sides of the respective lock portions j situatedtowards the respective support portions q, that is, at the sides facingtheir respective other lock portions j. The pins are cam followers t′which come into contact with the cams y for rotating the lock portions j(see FIGS. 31 to 35).

When the tape cassette b is loaded into a tape drive device, aninsertion pin h of the tape drive device is inserted into a cassetteshell c from a rectangular hole g of the cassette shell c, and comesinto contact with an inclined surface p defining a pin insertion recesso of a slider i (see FIG. 26(B)).

When the insertion pin h is further inserted into the pin insertionrecess o of the slider i, the front end of the insertion pin h pushesthe inclined surface p, so that the slider i moves towards the backagainst the biasing force of the slide spring 1 (see FIG. 27).

The cam followers t′ and t′ of the respective lock portions j and j comeinto contact with the respective cams y and y, and move towards the backalong the cams y and y, so that the lock portions j and j rotate in thedirection in which the anchoring pawls r and r move towards each other.By this, the anchoring pawls r and r of the respective lock portions jand j move away from the respective tape reels e and e, so that the tapereels e and e are unlocked, and are brought into a rotatable state (seeFIGS. 31 to 35).

FIGS. 31 to 35 are enlarged plan views showing states of the reel lockmechanism a′ in which a tape reel e changes from a locked state to anunlocked state.

The reel lock mechanisms a and a′ of the above-described related tapecassettes b have the following problems {circle around (1)} to {circlearound (3)}.

{circle around (1)} The tape cassette b cannot be reduced in size.

{circle around (2)} The elastic force of the lock spring k cannot bemade small, so that the tape reels cannot be stably locked.

{circle around (3)} When the tape reels e are unlocked, the tape reels erotate in the direction in which the magnetic tape d is made slack, sothat the magnetic tape d may become entangled with a member of the tapedrive device.

First, problem {circle around (1)} will be explained with reference tothe related reel lock mechanism a described earlier.

When the tape cassette b is made small, there is a problem in that therelated reel lock mechanism a cannot be disposed in a small triangularspace.

In other words, when the tape cassette b is reduced in size, thetriangular space naturally becomes smaller, so that the sliding amountof the slider i becomes smaller. On the other hand, the amount ofdisplacement of the anchoring pawls r and r of the respective lockportions j and j required to unlock the tape reels e and e (distance ofmovement of the anchoring pawls r and r away from the respective tapereels e and e) do not change very much even if the tape cassette bbecomes smaller, so that the amount of displacement needs to besubstantially the same as the amount of displacement of the anchoringpawls r and r of the related reel lock mechanism a.

Therefore, in order to make the amount of displacement of the anchoringpawls r the same regardless of a reduction in the sliding amount of theslider i, the pressure angles between the cams y and the respective camfollowers t must be made large. When the pressure angles are increased,a large force needs to be exerted upon the cam followers t in order torotate the respective lock portions j, so that the slider i and the lockportions j cannot move smoothly. As a result, stable locking andunlocking of the tape reels e cannot be performed.

The pressure angles are angles formed at portions of contact of therespective cams y and their respective cam followers t by normal linesT1 to the cams y and movement directions T2 of the cam followers t(directions of tangential lines to the cam followers t with respect torotational centers O) (see FIGS. 29 and 30).

FIGS. 29 and 30 are schematic views for comparing the relationshipsbetween the pressure angles and the sliding amount of the slider i whenthe amount of displacement of the anchoring pawls r of their respectivelock portions j is made constant.

FIG. 29 schematically shows the relationships in the related reel lockmechanism a, in which, when the sliding amount of the slider i is σ andthe displacement amount of the anchoring pawls is δ, the pressure anglesbetween the cams y and the corresponding cam followers t are α.

On the other hand, FIG. 30 shows the relationships in the reel lockmechanism where the sliding amount of the slider i is reduced due to asize reduction in the tape cassette b. Here, in the case where thesliding amount of the slider i is reduced to σ′, which is substantiallyhalf the sliding amount σ of the slider i shown in FIG. 29, when thedisplacement amount of the anchoring pawls r of the lock portions j arekept equal to the displacement amount δ, the pressure angles between thecams y and the respective cam followers t become α′.

Therefore, it can be understood that, when the sliding amount of theslider i becomes smaller due to a size reduction of the tape cassette b,the pressure angles between the cams y and the respective cam followerst become large (α′>α), so that the reel lock mechanism a either cannotmove smoothly or cannot easily move smoothly.

Problem {circle around (2)} will be explained with reference to therelated reel lock mechanism a. The lock portions j are supported by theslider i in a cantilever manner, so that, when they are subjected toshock, they tend to rotate with the support portions q as centers.Therefore, a larger force is required to keep the tape reels e in alocked state.

More specifically, the lock portions j of the reel lock mechanism a aresupported at the support portions q at one end of the lock portions j bythe support shafts m of the slider i. Therefore, in the case where theanchoring pawls r are engaged with and locked at an engaging tooth f andan engaging tooth f of the respective tape reels e, if a shock isexerted upon the lock portions j when, for example, the tape cassette bis dropped, the lock portions j try to rotate with the support portionsq as centers. When the tape cassette b is dropped, a shock of 500 G to1000 G is ordinarily exerted, so that a large rotational force isgenerated at the lock portions j supported in a cantilever manner.

Obviously, it is necessary to assume that the tape cassette b may bedropped at the time the tape cassette b is being designed. Thus, it isnecessary to design the tape cassette b so that the lock spring k has ahigh elastic force in order to prevent the tape reels from becomingunlocked when the tape cassette b is dropped.

Therefore, the contact pressures between the cams y and the respectivecam followers t become larger, so that repeated sliding causes seriouswearing of the contact surfaces of the cams y and the respective camfollowers t, thereby causing both contact surfaces to become rough. Thisresults in the problem of making it more difficult to smoothly move thereel lock mechanism a.

In order to prevent this, for example, the pressure angles may be madesmaller, or the coefficient of friction between the materials of thecontact surfaces may be made smaller. However, the former goes againstsize reduction of the tape cassette b as mentioned above, and the latterresults in increased costs, so that these cannot serve as solutions.

Problem {circle around (3)} is described with reference to the relatedreel lock mechanism a′. When the tape reels e are unlocked, the tapereels e rotate in the direction in which the magnetic tape d becomesslack, so that the portion of the magnetic tape d outside the cassetteshell c becomes slack. Accordingly, after loading the tape cassette binto the tape drive device, the slack magnetic tape d may cause troublessuch as the tape path not being properly formed or the magnetic tape dbecoming entangled with a member of the tape drive device.

Each tape reel e is in a locked state when the front end of itsanchoring pawl r is positioned at a corner of a recess f1 of each tapereel e situated at a side towards which each tape reel e winds up themagnetic tape d (this direction hereinafter referred to as “forward,”and the opposite direction hereinafter referred to as “backward” interms of the tape reels 3) (see FIG. 31). In this state, when the slideri moves backward, each anchoring pawl r is caught by a protrusion f2behind the adjacent recess f1 where the anchoring pawl r is positioned(in FIG. 32, the anchoring pawl r is shown as being caught by theprotrusion f2 marked with a dot) (see FIG. 32). Further backwardmovement of the slider i causes each protrusion f2 which has caught itsanchoring pawl r to move backward, so that each tape reel e rotates inthe direction in which the magnetic tape d becomes slack (see FIG. 33).

Accordingly, the present invention makes it possible to overcome theabove-described problems {circle around (1)} to {circle around (3)} inorder to reduce the size of a tape cassette, to stabilize locking of atape reel, to prevent reverse rotation of the tape reel when the tapereel is unlocked to minimize slacking in a magnetic tape.

DISCLOSURE OF INVENTION

To overcome the above-described problems, the present invention providesa reel lock mechanism of a tape cassette for locking tape reels of thetape cassette having the tape reels upon which a tape-shaped recordingmedium is wound rotatably supported inside a cassette shell. The reellock mechanism comprises a slider which is disposed in a space betweenthe two tape reels and the inside surface of a back wall of the cassetteshell, and which is supported so as to be movable forward and backward;two lock portions which are rotatably supported at both the left andright sides of the slider; a slide spring for pushing the sliderforward; and a lock spring for biasing the lock portions in directionsin which the lock portions engage the respective tape reels. Loading ofthe tape cassette into a tape drive device causes the slider to withdrawand the lock portions to rotate in directions in which the lock portionsmove away from the respective tape reels in order to unlock the tapereels. Each lock portion has a front portion including an anchoring pawlwhich engages the tape reel and a back portion extending in a directionsubstantially opposite to the front portion with a support portionsupported by the slider serving as center. When the slider withdraws,the back portion of each lock portion comes into contact with the insidesurface of the back wall of the cassette shell and each lock portionrotates in an unlocking direction, so that each anchoring pawl separatesfrom the tape reel.

The present invention provides a tape cassette comprising a reel lockmechanism for locking tape reels of the tape cassette having the tapereels upon which a tape-shaped recording medium is wound rotatablysupported inside a cassette shell. The reel lock mechanism comprises aslider which is disposed in a space between the two tape reels and theinside surface of a back wall of the cassette shell, and which issupported so as to be movable forward and backward; two lock portionswhich are rotatably supported at both the left and right sides of theslider; a slide spring for pushing the slider forward; and a lock springfor biasing the lock portions in directions in which the lock portionsengage the respective tape reels. Loading of the tape cassette into atape drive device causes the slider to withdraw and the lock portions torotate in directions in which the lock portions move away from therespective tape reels in order to unlock the tape reels. Each lockportion has a front portion including an anchoring pawl which engagesthe tape reel and a back portion extending in a direction substantiallyopposite to the front portion with a support portion supported by theslider serving as center. When the slider withdraws, the back portion ofeach lock portion comes into contact with the inside surface of the backwall of the cassette shell and each lock portion rotates in an unlockingdirection, so that each anchoring paw!separates from the tape reel.

Accordingly, in the reel lock mechanism of tape reels and the tapecassette, since the reel lock mechanism is provided in a back wall sideportion, or wider portion, of the space between the two tape reels andthe inside surface of the back wall of the cassette shell, it ispossible to relatively easily design the reel lock mechanism in terms oforientations of the back portions of the lock portions from the supportportions. By this, it is possible to smoothly move the reel lockmechanism by reducing the contact angles between the back side portionsand the back wall, that is, the pressure angles.

Since the lock portions of the reel lock mechanism comprises supportportions and front and back portions extending in substantially oppositedirections from the support portions, even if a person accidentallydrops the tape cassette, rotational forces acting in opposite directionsare produced at the front and back portions, so that the rotationalforces acting in both directions cancel each other. Thus, rotationalforces are not produced at the lock portions as a whole. Even ifrotational forces are produced, the rotational forces can be made verysmall. Therefore, it is possible to reduce the contact pressures betweenthe back portions of the lock portions and the back wall by setting theelastic force of the lock spring small, thereby making it is possible toreduce wear of both contact surfaces of the back portions of the lockportions and the back wall, as a result of which the reel lock mechanismcan be smoothly operated for a long period of time. In addition, it isnot necessary to use a special material for the contact surfaces, sothat costs are not increased.

To overcome the above-described problems, the present invention providesanother reel lock mechanism of a tape cassette for locking tape reels ofthe tape cassette having the tape reels upon which a tape-shapedrecording medium is wound rotatably supported inside a cassette shell.The reel lock mechanism comprises a slider which is disposed in a spacebetween the two tape reels and the inside surface of a back wall of thecassette shell, and which is supported so as to be movable forward andbackward; two lock portions which are rotatably supported at both theleft and right sides of the slider; a slide spring for pushing theslider forward; and a lock spring for biasing the lock portions indirections in which the lock portions engage the respective tape reels.Engagement of an engaging pawl of each lock portion with engaging teethof the tape reel by a forward movement of the slider causes each tapereel to be locked, or, loading of the tape cassette into a tape drivedevice causes the slider to withdraw and each lock portion to rotateaway from the tape reel, so that each tape reel is unlocked. Theengaging teeth are formed by recesses and protrusions alternatelyprovided at the peripheral edge of each tape reel, with the bottomsurface defining each recess having a central portion which protrudes ina chevron shape or a corner of each protrusion having an inclinedsurface. An end portion of each anchoring pawl has a flat surface thatcomes into contact with one inclined surface of the bottom surfacedefining a recess and an inclined surface of a protrusion disposedadjacent to the one inclined surface of the bottom surface defining therecess through another inclined surface of the bottom surface definingthe recess, the inclined surface of the protrusion being situatedadjacent the recess.

The present invention provides another tape cassette comprising a reellock mechanism for locking tape reels of the tape cassette having thetape reels upon which a tape-shaped recording medium is wound rotatablysupported inside a cassette shell. The reel lock mechanism comprises aslider which is disposed in a space between the two tape reels and theinside surface of a back wall of the cassette shell, and which issupported so as to be movable forward and backward; two lock portionswhich are rotatably supported at both the left and right sides of theslider; a slide spring for pushing the slider forward; and a lock springfor biasing the lock portions in directions in which the lock portionsengage the respective tape reels. Engagement of an engaging pawl of eachlock portion with engaging teeth of the tape reel by a forward movementof the slider causes each tape reel to be locked, or, loading of thetape cassette into a tape drive device causes the slider to withdraw andeach lock portion to rotate, so that each tape reel is unlocked. Theengaging teeth are formed by recesses and protrusions alternatelyprovided at the peripheral edge of each tape reel, with the bottomsurface defining each recess having a central portion which protrudes ina chevron shape or a corner of each protrusion having an inclinedsurface. An end portion of each anchoring pawl has a flat surface thatcomes into contact with one inclined surface of the bottom surfacedefining a recess and an inclined surface of a protrusion disposedadjacent to the one inclined surface of the bottom surface defining therecess through another inclined surface of the bottom surface definingthe recess, the inclined surface of the protrusion being situatedadjacent the recess.

Accordingly, with regard to the different reel lock mechanism of tapereels and the different tape cassette of the invention, when the slideris moved backward as a result of loading the tape cassette into a tapedrive device, the anchoring pawls of the respective lock portions arenot caught by the protrusions of the engaging teeth of the tape reels,so that the tape reels are not rotated when the lock portions withdraw,thereby keeping the tape-shaped recording medium in a tensioned state.

Therefore, when the tape cassette is loaded into a tape drive device, itis possible to prevent, for example, improper formation of a tape pathor entangling of the tape-shaped recording medium with a member of thetape drive device by a slack in the tape-shaped recording medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates, along with FIGS. 2 to 10, a tape cassette and a reellock mechanism of the tape cassette of a first embodiment of the presentinvention. These figures are schematic perspective views showing thetape cassette from the front side thereof.

FIG. 2 is a schematic perspective view showing the tape cassette fromthe back side thereof.

FIG. 3 is an enlarged perspective view of the reel lock mechanism.

FIG. 4 is an enlarged exploded perspective view of the reel lockmechanism.

FIG. 5 is a schematic plan view showing a state in which a top shell ofthe tape cassette is removed.

FIGS. 6(A) and 6(B) illustrate, along with FIGS. 7 to 9, the movementsof the reel lock mechanism in turn. FIGS. 6(A) and 6(B) are an enlargedplan view and an enlarged sectional view thereof, respectively, and showa locked state of a tape reel.

FIGS. 7(A) and 7(B) illustrate a state in which a cam follower is incontact with a cam.

FIGS. 8(A) and 8(B) illustrate a state in which a lock portion isseparated from the tape reel.

FIGS. 9(A) and 9(B) illustrate a state in which the tape reel iscompletely unlocked.

FIG. 10 is a schematic plan view for illustrating a pressure angle.

FIG. 11 illustrates, along with FIGS. 12 to 22, a tape cassette and areel lock mechanism of the tape cassette of a second embodiment of thepresent invention, and is a schematic perspective view of the tapecassette from the front side thereof.

FIG. 12 is a schematic perspective view of the tape cassette from theback side thereof.

FIG. 13 is a schematic plan view showing a state in which a top shell ofthe tape cassette is removed.

FIG. 14 is an enlarged perspective view of the reel lock mechanism.

FIG. 15 is an enlarged exploded perspective view of the reel lockmechanism.

FIG. 16 is, along with FIG. 17, a schematic vertical sectional viewshowing in enlarged form the reel lock mechanism, and shows a lockedstate.

FIG. 17 shows an unlocked state.

FIG. 18 is, along with FIGS. 19 to 22, an enlarged plan view showing themovements of the reel lock mechanism in turn, and shows a locked state.

FIG. 19 shows a state in which a flat surface of an anchoring pawl is incontact with one inclined surface defining a recess between engagingteeth and one tapered surface of a protrusion as a result of slightwithdrawal of a lock portion from the position shown in FIG. 18.

FIG. 20 shows a state in which the flat surface of the anchoring pawl isin contact with only the one tapered surface of the protrusion of theengaging tooth as a result of slight withdrawal of the lock portion fromthe position shown in FIG. 19.

FIG. 21 shows a state in which a cam follower is in contact with a camas a result of withdrawal of the lock portion from the position shown inFIG. 20.

FIG. 22 shows a state in which a tape reel is completely unlocked as aresult of withdrawal of the lock portion from the position shown in FIG.21.

FIG. 23 illustrates, along with FIGS. 24 to 30, a related reel lockmechanism, and is an enlarged perspective view thereof.

FIG. 24 is an enlarged exploded perspective view of the reel lockmechanism.

FIGS. 25(A) and 25(B) illustrate, along with FIGS. 26 to 28, themovements of the reel lock mechanism in turn. FIGS. 25(A) and 25(B) arean enlarged plan view and an enlarged sectional view thereof,respectively, and show a locked state of the tape reel.

FIGS. 26(A) and 26(B) show a state in which a cam follower is in contactwith a cam.

FIGS. 27(A) and 27(B) show a state in which a lock portion is separatedfrom the tape reel.

FIGS. 28(A) and 28(B) show a completely unlocked state.

FIG. 29 illustrates, along with FIG. 30, a pressure angle, and is aschematic plan view for illustrating the pressure angle of the relatedreel lock mechanism.

FIG. 30 is a schematic plan view for illustrating the pressure anglewhen the related reel lock mechanism is reduced in size.

FIG. 31 is, along with FIGS. 32 to 35, an enlarged plan view forillustrating the movements of another related reel lock mechanism inturn, and shows a locked state.

FIG. 32 shows a state in which an engaging pawl is caught by aprotrusion as a result of slight withdrawal of a lock portion from theposition shown in FIG. 31.

FIG. 33 shows a state in which the tape reel is rotated by causing theengaging pawl to be caught by a protrusion as a result of slightwithdrawal of the lock portion from the position shown in FIG. 32.

FIG. 34 shows a state in which a cam follower is in contact with a camas a result of withdrawal of the lock portion from the position shown inFIG. 33.

FIG. 35 shows a completely unlocked state as a result of withdrawal ofthe lock portion from the position shown in FIG. 34.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereunder, a reel lock mechanism of a tape cassette and a tape cassetteusing the reel lock mechanism will be given described in accordance witheach embodiment shown in the attached drawings.

FIGS. 1 to 10 illustrate a reel lock mechanism of a tape cassette and atape cassette using the reel lock mechanism of a first embodiment of thepresent invention.

A tape cassette 1 comprises a cassette shell 4 formed by a top shell 2and a bottom shell 3. Two tape reels 6 and 6 upon which a magnetic tape5 is wound are rotatably accommodated inside the cassette shell 4. Aplurality of engaging teeth 7, 7, . . . , serving as protrusions, areformed at the peripheral edges of lower flanges 6′ and 6′ of therespective tape reels 6 and 6, with recesses being formed therebetween(see FIGS. 1, 2, and 5).

A front lid 8 for covering the front surface of the magnetic tape 5positioned along the front surface of the cassette shell 4 is rotatablysupported at the front end of the cassette shell 4 (see FIGS. 1 and 2).

A reel lock mechanism 9 is provided in a substantially triangular space(hereinafter referred to as “the triangular space”), defined by a backwall 10 and the two tape reels 6 and 6, inside the cassette shell 4. Arectangular hole 12 is formed in a portion of the bottom surface of thebottom shell 3 where the reel lock mechanism 9 is situated. When thetape cassette 1 is loaded into a tape drive device, an insertion pin 13,provided at the tape drive device, is inserted into the cassette shell 4from the rectangular hole 12, and acts on the reel lock mechanism 9 inorder to unlock the tape reels 6 and 6 (see FIGS. 6 to 9).

The reel lock mechanism 9 comprises a slider 14, two lock portions 15and 15, a lock spring 16, and a slide spring 17 (see FIGS. 3 and 4).

The slider 14 is disposed so as to be movable forward and backward atthe bottom shell 3. Upwardly protruding support shafts 18 and 18, whichare separated in the leftward and rightward directions, are provided atthe back end of the slider 14. A placement recess 19, which opens upwardand backward, is formed between the support shafts 18 and 18 of theslider 14 (see FIGS. 3, 4, and 5).

A pin insertion recess 20, which opens at the bottom surface, forinserting the insertion pin 13 of the tape drive device is formed in aportion of the slider 14 situated forwardly of the placement recess 19,and the lower half of the back surface defining the pin insertion recess20 is an inclined surface 21 which is displaced backward as it extendsdownward (see FIGS. 6 to 9).

Two lock portions 15 and 15 are symmetrical in form, and havesubstantially chevron shapes as a whole in plan view. Verticallyextending cylindrical support portions 22 and 22 are integrally formedwith bent portions of the respective lock portions 15 and 15. Portions23 and 23 of the respective lock portions 15 and 15 situated forwardlyof the respective support portions 22 and 22 (hereinafter referred to as“the front portions”) extend away from each other, with taperedanchoring pawls 24 and 24 being formed at the front ends of the frontportions 23 and 23 (see FIGS. 23 and 24).

Portions 25 and 25 of the two lock portions 15 and 15 situated behindthe support portions 22 and 22 (hereinafter referred to as “the backportions”) extend away from each other, with the back ends of the backportions 25 and 25 being cam followers 26 and 26 which come into contactwith the back wall 10 of the cassette 4 in order to rotate the lockportions 15 and 15 in opposite directions. Spring catch portions 27 and27 are integrally formed with the top side edges of the respective lockportions 15 and 15 between the support portions 22 and 22 and therespective anchoring pawls 26 and 26 (see FIGS. 3 and 4).

Externally fitting the support portions 22 to support shafts 18 of theslider 14 rotatably supports the lock portions 15 by the slider 14. Inthis way, the lock portions 15 are formed so that the front portions 23and the back portions 25 extend in substantially opposite directionswith the support portions 22 serving as centers (see FIG. 5).

The lock spring 16 is a torsion coil spring, in which coil portions 28and 28, a linking portion. 29 linking the coil portions 28 and 28, andengaging portions 30 and 30 are integrally formed, with the coilportions 28 and 28 being separated in the leftward and rightwarddirections and the engaging portions 30 and 30 protruding from theirrespective coil portions 28 and 28 and being positioned outwardly of thelinking portion 29. The two coil portions 28 and 28 are supported attheir respective support shafts 18 and 18 by being externally fitted tothe top sides of the support portions 22 and 22 of their respective lockportions 15 and 15. The two engaging portions 30 and 30 engage thespring catch portions 27 and 27 of the two lock portions 15 and 15, sothat the two lock portions 15 and 15 are biased in the directions inwhich the anchoring pawls 24 and 24 move away from each other, that is,in the directions in which the anchoring pawls 24 and 24 engage anengaging tooth 7 and an engaging tooth 7 of the respective tape reels 6and 6 (see FIG. 4).

The slide spring 17 is a helical compression spring, and is provided ina compressed manner between the inside surface of the back wall 10 ofthe cassette shell 4 and the placement recess 19 of the slider 14. Bythis, the slider 14 is biased forward (see FIGS. 6 to 9).

Portions of the back wall 10 of the cassette shell 4 at the left andright sides of the portion of the back wall 10 situated incorrespondence with the slider 14 are portions with which the camfollowers 26 and 26 of the respective lock portions 15 and 15 come intocontact and along which they slide, and are cams 31 and 31 forcontrolling rotation of the lock portions 15 and 15.

When the tape cassette 1 is not loaded into a tape drive device, theslider 14 is biased maximally in the forward direction by the biasingforce of the slide spring 17, and the cam followers 26 and 26 of therespective lock portions 15 and 15 are separated from the respectivecams 31 and 31, so that the anchoring pawls at the front ends of therespective lock portions 15 and 15 are rotated in the directions inwhich they move away from each other, and the engaging pawls 24 and 24engage an engaging tooth f and an engaging tooth f of the respectivetape reels 6 and 6. By this, the tape reels 6 and 6 are brought into alocked state, that is, in a state in which the tape reels 6 and 6 areprevented from rotating (see FIG. 6).

The lock portions 15 include anti-rotation means (not shown), and aresuch that they do not rotate beyond a predetermined angle in thedirections in which they engage the engaging teeth 7 of the tape reels.More specifically, when the slider 14 is situated slightly behind theforemost end of its movement range, the rotational angles of the lockportions 15 are angles of the order in which the front ends of theanchoring pawls 24 of the respective lock portions 15 contact the outerperipheral edges of lower flanges 6′ of the respective tape reels 6. Inthe state shown in FIG. 7, the rotation of the anchoring pawls 24 arerestricted by the anti-rotation means, so that the anchoring pawls 24 donot move towards the respective tape reels 6.

The rotation of the lock portions 15 and 15 towards their respectivetape reels 6 and 6 are restricted by their respective anti-rotationmeans. When the slider moves to the foremost end of its movement range,the anchoring pawls 24 and 24 of the respective lock portions 15 and 15that are disposed towards the center of the tape cassette 1 engage anengaging tooth 7 and an engaging tooth 7 of the tape reels 6 and 6, sothat the tape reels 6 and 6 become locked.

Since the slider 14 is biased forward, a rotational force is applied tothe two tape reels 6 and 6 through the respective anchoring pawls 24 and24 in the direction in which the magnetic tape 5 is tensioned, so thatthe magnetic tape 5 is maintained in a tensioned state when the tapereels 6 and 6 are locked (see FIG. 6).

When the tape cassette 1 is loaded into a tape drive device, theinsertion pin 13 of the tape drive device is inserted into the cassetteshell 4 from the rectangular hole 12 of the cassette shell 4, and comesinto contact with the inclined surface 21 defining the pin insertionrecess 20 of the slider 14 (see FIG. 7).

When the insertion pin 13 is further inserted into the pin insertionrecess 20 of the slider 14, the front end of the insertion pin 13 pushesthe inclined surface 21, so that the slider 14 moves towards the backagainst the biasing force of the slide spring 17 (see FIG. 8).

When the cam followers 26 and 26 of the respective lock portions 15 and15 come into contact with the cams 31 and 31 of the back wall 10 of thecassette shell 4 (see FIG. 7), the cam followers 26 and 26 arerelatively pushed by the respective cams 31 and 31.

By this, the cam followers 26 and 26 move away from each other whilesliding along the respective cams 31 and 31, so that the lock portions15 and 15 rotate.

The lock portions 15 and 15 rotate so that the anchoring pawls 24 and 24at the front ends of the lock portions 15 and 15 move towards eachother, so that the anchoring pawls 24 and 24 move away from therespective tape reels 6 and 6, causing the tape reels 6 and 6 to beunlocked and to become rotatable (see FIG. 9).

FIG. 10 is an enlarged view showing a state in which a cam follower 26is in contact with a cam 31. It can be seen that, when an angle formedby a normal line T1 to the cam 31 and a movement direction T2 of the camfollower 26 (direction of a tangential line to the cam follower 26 withrespect to rotational center O), that is, a pressure angle is α, thepressure angle α is small, so that the slider 14 moves smoothly, thatis, the sliding resistance between the cam follower 26 and the cam 31,or the resistance to the movement of the slider 14, is small.

The back portions 25 of the respective lock portions 15 extend in awider portion of the triangular space 11 situated towards the back wall10, so that it is possible to relatively easily design the reel lockmechanism in terms of orientations of the back portions 25 of the lockportions 15 from the support portions 22. Therefore, it is possible tofurther reduce the pressure angle.

The cams 31 and 31 may be formed as inclined surfaces that are displacedbackward as they extend outward, that is, as they extend towards theleft and right from the center, so that the pressure angles between thecam followers 26 and 26 and the respective cams 31 and 31 can be furtherreduced.

In this way, providing the cams 31 and the cam followers 26 in theback-wall-10-side portion of the triangular space increases the freedomwith which the reel lock mechanism is designed in terms of pressureangle, so that the reel lock mechanism 9 can move smoothly.

When the tape cassette 1 is accidentally dropped, the lock portions 15upon which shock is exerted tend to rotate. Since the front portions 23and the back portions 25 are formed so that they extend in oppositedirections with the respective support portions 22 as rotationalcenters, rotational forces acting in opposite directions are produced atthe front portions 23 and the respective back portions 25, so that therotational forces acting in both directions cancel each other. Thus,rotational forces are not produced at the lock portions 15 and 15 as awhole. Even if rotational forces are produced, the rotational forces canbe made very small, so that the tape reels 6 and 6 do not becomeunlocked.

Therefore, even if the tape cassette 1 is dropped, the lock portions 15and 15 do not rotate due to, for example, dropping shock. Consequently,it is possible to reduce elastic force of the lock spring 16. By settingthe elastic force of the lock spring 16 small, the contact pressuresbetween the cams 31 and the respective cam followers 26 can be madesmall, thereby making it is possible to reduce wear of both contactsurfaces of the cams 31 and the respective cam followers 26, as a resultof which the reel lock mechanism 9 can be smoothly moved for a longperiod of time. In addition, it is not necessary to use a specialmaterial for the contact surfaces, so that costs are not increased.

Next, a reel lock mechanism of a tape cassette and a tape cassette usingthe reel lock mechanism of a second embodiment of the present inventionwill be described with reference to FIGS. 11 to 22.

A tape cassette 101 comprises a cassette shell 104 formed by a top shell102 and a bottom shell 103. Two tape reels 106 and 106 upon which amagnetic tape 105 is wound are rotatably accommodated inside thecassette shell 104. A plurality of engaging teeth 107, 107, . . . , areformed at the peripheral edges of lower flanges 106′ and 106′ of therespective tape reels 106 and 106 (see FIGS. 11 to 13).

The engaging teeth 107, 107, . . . , are formed by recesses andprotrusions that are alternately formed at the peripheral edge of eachtape reel 106.

The shapes of the engaging teeth 107, 107, . . . , will be specificallydescribed. Bottom surfaces 109 defining recesses 108 have centralportions protruding into chevron shapes. Both corners of each protrusion110 have inclined surfaces (hereinafter referred to as “the taperedsurfaces”) 110′ and 110′. As described later, the recesses 108 and theprotrusions 110 forming the engaging teeth 107 are formed symmetricallyin radial directions extending through their respective centers. The twotape reels 106 and 106 (supply reel and take-up reel) have the sameshapes (see FIGS. 18 to 22).

One tapered surface 110′, which is disposed at a side that contacts aninclined surface 109″, of a protrusion 110 (marked with a dot in therelevant figures) adjacent one inclined surface 109′ of a chevron-shapedbottom surface 109, defining a recess 108, through the other inclinedsurface 109″, and the one inclined surface 109′ are formed so as to bepositioned in substantially the same plane. As mentioned above, therecess 108 and the protrusion 110 are both formed symmetrically inradial directions. Therefore, the one inclined surface 109′ and theother inclined surface 109″ defining the recess 108 are formed with thesame angles of inclination in the radial directions. Further, the onetapered surface 110′ and the other tapered surface 110″ of theprotrusion 110 are formed with the same angles of inclination in theradial directions (see FIGS. 18 to 22).

The widths of the recesses 108 and the protrusions 110 in thecircumferential direction do not need to be the same.

A front lid 111 for covering the front surface of the magnetic tape 105positioned along the front surface of the cassette shell 104 isrotatably supported at the front end of the cassette shell 104 (seeFIGS. 11 and 12).

A reel lock mechanism 112 is provided in a substantially triangularspace (hereinafter referred to as “the triangular space”), defined by aback wall 113 and the two tape reels 106 and 106, inside the cassetteshell 104. A rectangular hole 115 is formed in a portion of the bottomsurface of the bottom shell 103 where the reel lock mechanism 112 issituated. When the tape cassette 101 is loaded into a tape drive device,an insertion pin 116, provided at the tape drive device, is insertedinto the cassette shell 104 from the rectangular hole 115 (see FIGS. 16and 17), and acts on the reel lock mechanism 112 in order to unlock thetape reels 106 and 106 (see FIGS. 18 to 22).

The reel lock mechanism 112 comprises a slider 117, two lock portions118 and 118, a lock spring 119, and a slide spring 120 (see FIGS. 14 and15).

The slider 117 is disposed so as to be movable forward and backward atthe bottom shell 103. Upwardly protruding support shafts 121 and 121,which are separated in the leftward and rightward directions, areprovided at the back end of the slider 117. A placement recess 122,which opens upward and backward, is formed between the support shafts121 and 121 of the slider 117 (see FIGS. 13 to 15).

A pin insertion recess 123, which opens at the bottom side thereof, forinserting the insertion pin 116 of the tape drive device is formed in aportion of the slider 117 situated forwardly of the placement recess122, and the lower half of the back surface defining the pin insertionrecess 123 is an inclined surface 124 which is displaced backward as itextends downward (see FIGS. 16 to 17).

The two lock portions 118 and 118 are formed symmetrically, each beingone plate-shaped member having a substantially chevron shape as a wholein plan view. Vertically extending cylindrical support portions 125 and125 are formed integrally with the back ends of the respectiveplate-shaped members. The front end portions of the two lock portions118 and 118 extend away from each other. Tapered anchoring pawls 126 and126 are formed at the front ends of the respective lock portions 118 and118 (see FIGS. 14 and 15 and FIGS. 18 to 22).

A surface 127 of each anchoring pawl 126 facing its corresponding tapereel 106 is a flat surface. The width of each flat surface 127 in theforward-and-backward directions is larger than the distance between oneinclined surface 109′ of each recess 108 between adjacent engaging teeth107 formed so as to be positioned in substantially the same plane andone tapered surface of each protrusion 110 adjacent the inclined surface109′ through the other inclined surface 109″.

Spring catch portions 129 are integrally formed with the top side edgesof the respective lock portions 118 between the support portions 125 andthe respective anchoring pawls 126. Lower side edges of the respectivelock portions 118 have forms in which the front side portions thereofprotrude downward from substantially the longitudinal centers of thelower side edges of the. respective lock portions 118. The back edges ofthe respective downwardly protruding portions are cam followers 130which come into contact with respective cams (described later) forrotating the respective lock portions 118 (see FIGS. 14 and 15 and FIGS.18 to 22). Externally fitting the support portions 125 and 125 to theirrespective support shafts 121 and 121 of the slider 117 rotatablysupports the lock portions 118 and 118 at the slider 117 (see FIGS. 14and 15).

The lock spring 119 is a torsion coil spring, in which coil portions 131and 131, a linking portion 132 linking the coil portions 131 and 131,and engaging portions 133 and 133 are integrally formed, with the coilportions 131 and 131 being separated in the leftward and rightwarddirections and the engaging portions 133 and 133 protruding from theirrespective coil portions 131 and 131 and being positioned outwardly ofthe linking portion 132. The two coil portions 131 and 131 are supportedat their respective support shafts 121 and 121 by being externallyfitted to the top sides of the support portions 125 and 125 of theirrespective lock portions 118 and 118. The two engaging portions 133 and133 engage the spring catch portions 129 and 129 of the two lockportions 118 and 118, so that the two lock portions 118 and 118 arebiased in the directions in which the anchoring pawls 126 and 126 moveaway from each other, that is, in the directions in which the anchoringpawls 126 and 126 engage an engaging tooth 107 and an engaging tooth 107of the respective tape reels 106 and 106 (see FIG. 14).

The slide spring 120 is a helical compression spring, and is provided ina compressed manner between the inside surface of the back wall 113 ofthe cassette shell 104 and the placement recess 122 of the slider 117.By this, the slider 117 is biased forward (see FIGS. 16 and 17, andFIGS. 18 to 22).

Ribs 134 and 134 having small heights measured from the bottom surfaceare provided in a standing manner on both the left and right sides ofthe slider 117 inside the cassette shell 104. In plan view, the ribs 134and 134 comprise portions extending in the direction in which the slider117 slides, portions which move along an arc one size larger than theouter peripheral edges of the respective tape reels 106 and 106, andportions which are located in the paths of movement of the respectivelock portions 118 and 118. Of these portions, the portions located inthe paths of movement of the respective lock portions 118 and 118, morespecifically, the portions situated in correspondence with therespective cam followers 130 and 130 are cams 135 and 135 forcontrolling rotation of the respective lock portions 118 and 118 (seeFIGS. 14 and 15).

Next, a description of the movement of the reel lock mechanism 112 willbe given. FIGS. 16 and 17 are enlarged sectional views of the mainportion of the reel lock mechanism 112, and FIGS. 18 to 22 are enlargedplan views of the main portion of the reel lock mechanism 112. FIGS. 16and 18 show a state in which a tape reel lock 106 is locked. FIGS. 17and 22 show a state in which the tape reel 106 is completely unlocked.Hereunder, a description of changes in states of the tape reels from thelocked state to the unlocked state will be given with reference to FIGS.18 to 22.

FIGS. 16 and 18 show a state in which the tape reels 106 and 106 arelocked by the reel lock mechanism 112 when the tape cassette 101 is notloaded in a tape drive device.

In the state shown in FIGS. 16 and 18, the slider 117 is positioned atthe front end of its range of movement by being biased by the slidespring 120, and the lock portions 118 and 118 are rotated in thedirections in which the anchoring pawls 126 and 126 move away from eachother and are positioned inside recesses 108 and 108 between adjacentengaging teeth 107 and 107 of the respective tape reels 106 and 106, sothat the tape reels 106 and 106 are in a locked state (see FIG. 18).

The lock portions 118 and 118 include anti-rotation means, and are suchthat they do not rotate beyond a predetermined angle in the directionsin which they engage the engaging teeth 107 and 107 of the tape reels106 and 106. More specifically, when the slider 117 is situated slightlybehind the foremost end of its movement range, the lock portions 118 and118 are rotated to angles of the order in which the front ends of theanchoring pawls 126 and 126 of the respective lock portions 118 and 118contact the outer peripheral edges of lower flanges 106′ and 106′ of therespective tape reels 106 and 106, and the flat surfaces 127 and 127 ofthe respective anchoring pawls 126 and 126 substantially face the samedirections in the forward-and-backward directions. In the state shown inFIGS. 18 to 20, the rotation of the anchoring pawls 126 and 126 isrestricted by the anti-rotation means, so that the anchoring pawls 126and 126 do not move towards the respective tape reels 106 and 106.

Since the slider 117 is biased forward, a rotational force is applied tothe two tape reels 106 and 106 through the respective anchoring pawls126 and 126 in the direction in which the magnetic tape 105 istensioned, so that the magnetic tape 105 is maintained in a tensionedstate when the tape reels 106 and 106 are locked (see FIG. 18).

As can be seen in FIG. 18, a front end 128′ of the flat surface 127 ofthe anchoring pawl 126 of each lock portion 118 is positioned at onecorner of the bottom surface of a recess 108 between adjacent engagingteeth 107 of each tape reel 106, and the flat surface 127 of eachanchoring pawl 126 is substantially in contact with one inclined surface109′ defining the recess 108.

When the tape cassette 101 is loaded into a tape drive device, theinsertion pin 116 of the tape drive device is inserted into the cassetteshell 104 from the rectangular hole 115 of the cassette shell 104, andcomes into contact with the inclined surface 124 defining the pininsertion recess 123 of the slider 117.

When the insertion pin 116 is further inserted into the pin insertionrecess 123 of the slider 117, the front end of the insertion pin 116pushes the inclined surface 124, so that the slider 117 moves towardsthe back against the biasing force of the slide spring 120 (see FIG.19).

When the slider 117 starts to withdraw, the front end 128′ of the flatsurface 127 of each anchoring pawl 126 separates from the aforementionedone corner. Each flat surface 127 slides along the one inclined surface109′ of the recess 108, so that a back end 128″ thereof comes intocontact with one tapered surface 110′ of a protrusion 110. This isbecause, as described above, one inclined surface 109′ of a recess 108and one tapered surface 110′ of a protrusion 110 adjacent to the oneinclined surface 109′ through the other inclined surface 109″ are formedso as to be positioned in substantially the same plane (see FIG. 19).

When the slider 117 withdraws further, the flat surface 127 of eachanchoring pawl 126 moves away from the one inclined surface 109′ of therecess 108, and is only in contact with the one tapered surface 110′ ofthe protrusion 110 (see FIG. 20).

In this way, when the lock portions 118 move backward, the anchoringpawls 126 are not caught by any of the protrusions 110 of the engagingteeth 107 of the respective tape reels 106. This is because, asmentioned above, the widths of the flat surfaces 127 of the respectiveanchoring pawls 126 in the forward-and-backward directions are largerthan the distance between the one inclined surfaces 109′ of the recesses108 of the respective anchoring teeth 107 and the tapered surfaces 110′of the protrusions 110 adjacent the inclined surfaces 109′ through theother inclined surfaces 109″, and the inclined surfaces 109′ and therespective tapered surfaces 110′ are positioned in substantially thesame plane.

As mentioned above, the lock portions 118 do not rotate the respectivetape reels 106 by catching them when they move backward as the slider117 withdraws (see FIG. 20), so that the magnetic tape 105 does notbecome slack. In FIGS. 18 to 22, it can be seen that the protrusion 110marked with a dot is not moving.

When the slider 117 withdraws further, the cam followers 130 and 130come into contact with their respective cams 135 and 135 (see FIG. 21),so that the lock portions 118 and 118 rotate in an unlocking direction,thereby causing the anchoring pawls 126 and 126 to separate from theirrespective tape reels 106 and 106.

When the slider 117 is in a maximally withdrawn state, the anchoringpawls 126 and 126 of the respective lock portions 118 and 118 arepositioned farthest from the tape reels 106 and 106, so that the tapereels 106 and 106 are unlocked, thereby allowing the tape reels 106 and106 to rotate inside the cassette shell 104.

The tape reels 106 and 106 are accommodated inside the cassette shell104.so as to be movable slightly towards the front and back and towardsthe left and right. FIG. 22 shows a state in which one of the tablereels 106 shown by alternate long and two short dashed lines is closestto the reel lock mechanism 112. In this state, the lock portions 118 and118 are rotated to positions where they do not interrupt the rotation ofthe respective tape reels 106.

In order to prevent reverse rotation of the tape reels 106 and 106 whenthe tape reels 106 and 106 are being unlocked, the engaging teeth of thetape reels may be formed with sawteeth shapes. However, when they areformed with such shapes, the two tape reels (supply reel and take-upreel) become symmetrical in form, so that the tape reels cannot beformed with the same shape.

In contrast, in the above-described tape cassette 101, the recesses 108and the protrusions 110 forming the engaging teeth 107 are formedsymmetrically in radial directions extending through the centers of therecesses 108 and the protrusions 110. Therefore, the two tape reels(supply reel and take-up reel) do not particularly need to be formed asspecial-purpose component parts, and can, thus,be formed as commonparts. Consequently, costs are not increased for forming a structurewhich provides the above-described advantages.

Specific forms and structures of each part in each of theabove-described embodiments are merely specific examples in carrying outthe present invention, so that the technical scope of the presentinvention is not to be construed as being restricted by these forms andstructures.

As is clear from the foregoing description, the present inventionprovides a reel lock mechanism of a tape cassette for locking tape reelsof the tape cassette having the tape reels upon which a tape-shapedrecording medium is wound rotatably supported inside a cassette shell.The reel lock mechanism comprises a slider which is disposed in a spacebetween the two tape reels and the inside surface of a back wall of thecassette shell, and which is supported so as to be movable forward andbackward; two lock portions which are rotatably supported at both theleft and right sides of the slider; a slide spring for pushing theslider forward; and a lock spring for biasing the lock portions indirections in which the lock portions engage the respective tape reels.Loading of the tape cassette into a tape drive device causes the sliderto withdraw and the lock portions to rotate in directions in which thelock portions move away from the respective tape reels in order tounlock the tape reels. Each lock portion has a front portion includingan anchoring pawl which engages the tape reel and a back portionextending in a direction substantially opposite to the front portionwith a support portion supported by the slider serving as center. Whenthe slider withdraws, the back portion of each lock portion comes intocontact with the inside surface of the back wall of the cassette shelland each lock portion rotates in an unlocking direction, so that eachanchoring pawl separates from the tape reel.

The present invention provides a tape cassette comprising a reel lockmechanism for locking tape reels of the tape cassette having the tapereels upon which a tape-shaped recording medium is wound rotatablysupported inside a cassette shell. The reel lock mechanism comprises aslider which is disposed in a space between the two tape reels and theinside surface of a back wall of the cassette shell, and which issupported so as to be movable forward and backward; two lock portionswhich are rotatably supported at both the left and right sides of theslider; a slide spring for pushing the slider forward; and a lock springfor biasing the lock portions in directions in which the lock portionsengage the respective tape reels. Loading of the tape cassette into atape drive device causes the slider to withdraw and the lock portions torotate in directions in which the lock portions move away from therespective tape reels in order to unlock the tape reels. Each lockportion has a front portion including an anchoring pawl which engagesthe tape reel and a back portion extending in a direction substantiallyopposite to the front portion with a support portion supported by theslider serving as center. When the slider withdraws, the back portion ofeach lock portion comes into contact with the inside surface of the backwall of the cassette shell and each lock portion rotates in an unlockingdirection, so that each anchoring pawl separates from the tape reel.

Accordingly, in the reel lock mechanism of tape reels and the tapecassette, since the reel lock mechanism is provided in a back-wall-sideportion, or wider portion, of the space between the two tape reels andthe inside surface of the back wall of the cassette shell, it ispossible to relatively easily design the reel lock mechanism in terms oforientations of the back portions of the lock portions from the supportportions. By this, it is possible to smoothly move the reel lockmechanism by reducing the contact angles between the back side portionsand the back wall, that is, the pressure angles.

Since the lock portions of the reel lock mechanism comprises supportportions and front and back portions extending in substantially oppositedirections from the support portions, even if a person accidentallydrops the tape cassette, rotational forces acting in opposite directionsare produced at the front and back portions, so that the rotationalforces acting in both directions cancel each other. Thus, rotationalforces are not produced at the lock portions as a whole. Even ifrotational forces are produced, the rotational forces can be made verysmall. Therefore, it is possible to reduce the contact pressures betweenthe back portions of the lock portions and the back wall by setting theelastic force of the lock spring small, thereby making it is possible toreduce wear of both contact surfaces of the back portions of the lockportions and the back wall, as a result of which the reel lock mechanismcan be smoothly operated for a long period of time. In addition, it isnot necessary to use a special material for the contact surfaces, sothat costs are not increased.

The present invention provides another reel lock mechanism of a tapecassette for locking tape reels of the tape cassette having the tapereels upon which a tape-shaped recording medium is wound rotatablysupported inside a cassette shell. The reel lock mechanism comprises aslider which is disposed in a space between the two tape reels and theinside surface of a back wall of the cassette shell, and which issupported so as to be movable forward and backward; two lock portionswhich are rotatably supported at both the left and right sides of theslider; a slide spring for pushing the slider forward; and a lock springfor biasing the lock portions in directions in which the lock portionsengage the respective tape reels. Engagement of an engaging pawl of eachlock portion with engaging teeth of the tape reel by a forward movementof the slider causes each tape reel to be locked, or, loading of thetape cassette into a tape drive device causes the slider to withdraw andeach lock portion to rotate away from the tape reel, so that each tapereel is unlocked. The engaging teeth are formed by recesses andprotrusions alternately provided at the peripheral edge of each tapereel, with the bottom surface defining each recess having a centralportion which protrudes in a chevron shape or a corner of eachprotrusion having an inclined surface. An end portion of each anchoringpawl has a flat surface that comes into contact with one inclinedsurface of the bottom surface defining a recess and an inclined surfaceof a protrusion disposed adjacent to the one inclined surface of thebottom surface defining the recess through another inclined surface ofthe bottom surface defining the recess, the inclined surface of theprotrusion being situated adjacent the recess.

The present invention provides another tape cassette comprising a reellock mechanism for locking tape reels of the tape cassette having thetape reels upon which a tape-shaped recording medium is wound rotatablysupported inside a cassette shell. The reel lock mechanism comprises aslider which is disposed in a space between the two tape reels and theinside surface of a back wall of the cassette shell, and which issupported so as to be movable forward and backward; two lock portionswhich are rotatably supported at both the left and right sides of theslider; a slide spring for pushing the slider forward; and a lock springfor biasing the lock portions in directions in which the lock portionsengage the respective tape reels. Engagement of an engaging pawl of eachlock portion with engaging teeth of the tape reel by a forward movementof the slider causes each tape reel to be locked, or, loading of thetape cassette into a tape drive device causes the slider to withdraw andeach lock portion to rotate, so that each tape reel is unlocked. Theengaging teeth are formed by recesses and protrusions alternatelyprovided at the peripheral edge of each tape reel, with the bottomsurface defining each recess having a central portion which protrudes ina chevron shape or a corner of each protrusion having an inclinedsurface. An end portion of each anchoring pawl has a flat surface thatcomes into contact with one inclined surface of the bottom surfacedefining a recess and an inclined surface of a protrusion disposedadjacent to the one inclined surface of the bottom surface defining therecess through another inclined surface of the bottom surface definingthe recess, the inclined surface of the protrusion being situatedadjacent the recess.

Accordingly, with regard to the different reel lock mechanism of tapereels and the different tape cassette of the invention, when the slideris moved backward as a result of loading the tape cassette into a tapedrive device, the anchoring pawls of the respective lock portions arenot caught by the protrusions of the engaging teeth of the tape reels,so that the tape reels are not rotated when the lock portions withdraw,thereby keeping the tape-shaped recording medium in a tensioned state.

Therefore, when the tape cassette is loaded into a tape drive device, itis possible to prevent, for example, improper formation of a tape pathor entangling of the tape-shaped recording medium with a member of thetape drive device by a slack in the tape-shaped recording medium.

1. A reel lock mechanism for tape reels for locking the tape reels of atape cassette having the tape reels upon which a tape-shaped recordingmedium is wound rotatably supported inside a cassette shell, the reellock mechanism comprising: a slider which is disposed in a space betweenthe two tape reels and the inside surface of a back wall of the cassetteshell, the slider being supported so as to be movable forward andbackward; two lock portions which are rotatably supported at both theleft and right sides of the slider; a slide spring for pushing theslider forward; and a lock spring for biasing the lock portions indirections in which the lock portions engage the respective tape reels;wherein engagement of an engaging pawl of each lock portion withengaging teeth of the tape reel by a forward movement of the slidercauses each tape reel to be locked, or, loading of the tape cassetteinto a tape drive device causes the slider to withdraw and each lockportion to rotate away from the tape reel, so that each tape reel isunlocked; wherein the engaging teeth are formed by recesses andprotrusions alternately provided at the peripheral edge of each tapereel, with the bottom surface defining each recess having a centralportion which protrudes in a chevron shape or a corner of eachprotrusion having an inclined surface; and wherein an end portion ofeach anchoring pawl has a flat surface that comes into contact with oneinclined surface of the bottom surface defining a recess and an inclinedsurface of a protrusion disposed adjacent to the one inclined surface ofthe bottom surface defining the recess through another inclined surfaceof the bottom surface defining the recess, the inclined surface of theprotrusion being situated adjacent the recess.
 2. A tape cassettecomprising a reel lock mechanism for locking tape reels of the tapecassette having the tape reels upon which a tape-shaped recording mediumis wound rotatably supported inside a cassette shell, wherein the reellock mechanism comprises: a slider which is disposed in a space betweenthe two tape reels and the inside surface of a back wall of the cassetteshell, the slider being supported so as to be movable forward andbackward; two lock portions which are rotatably supported at both theleft and right sides of the slider; a slide spring for pushing theslider forward; and a lock spring for biasing the lock portions indirections in which the lock portions engage the respective tape reels;wherein engagement of an engaging pawl of each lock portion withengaging teeth of the tape reel by a forward movement of the slidercauses each tape reel to be locked, or, loading of the tape cassetteinto a tape drive device causes the slider to withdraw and each lockportion to rotate, so that each tape reel is unlocked; wherein theengaging teeth are formed by recesses and protrusions alternatelyprovided at the peripheral edge of each tape reel, with the bottomsurface defining each recess having a central portion which protrudes ina chevron shape or a corner of each protrusion having an inclinedsurface; and wherein an end portion of each anchoring pawl has a flatsurface that comes into contact with one inclined surface of the bottomsurface defining a recess and an inclined surface of a protrusiondisposed adjacent to the one inclined surface of the bottom surfacedefining the recess through another inclined surface of the bottomsurface defining the recess, the inclined surface of the protrusionbeing situated adjacent the recess.